1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device and, more particularly, to an LCD having a heat releasing structure for effectively releasing heat generated from heating elements such as an inverter IC (Integrated Circuit) and a transformer configured on a PCB (Printed Circuit Board).
2. Description of the Related Art
In general, an LCD is a device in which an optical anisotropy is changed by applying an electric field to liquid crystal assuming fluidity of liquid and crystalline optical properties. Compared with the conventional cathode ray tubes (CRTs), the LCD has low power consumption, a small volume, can be increased in size, and has high image resolution (minuteness or fineness).
However, the LCD is a light receiving device that displays images by adjusting the quantity of light received from the exterior, so it needs a light source, namely, a backlight unit, for emitting light to a liquid crystal panel. The backlight unit is divided into an edge type backlight unit and a direct type backlight unit depending on an installation position of a lamp.
Here, the edge type backlight unit includes a lamp installed at the side of a light guide plate that guides light. A lamp unit includes a lamp that emits light, a lamp holder inserted at both ends of the lamp to protect the lamp, and a lamp housing that covers an outer surface of the lamp and fixes the side of the light guide plate at one side surface thereof in order to reflect light emitted from the lamp toward the light guide plate.
The edge type backlight unit is commonly employed for relatively small LCD devices such as monitors of notebook computers and desktop computers, and has good light uniformity and long durability and is advantageous for making the LCD devices thinner.
The direct type backlight unit has been concentratively developed as the size of the LCDs has been increased. A plurality of lamps are arranged in a row on a lower surface of a diffusion plate and directly emit light to a front surface of a liquid crystal panel. The direct type backlight unit has a high light usage efficiency compared with the edge type backlight unit, so it is mainly used for a large-screen LCD that requires a high luminance.
The direct type backlight unit is divided into a light emitting part and a wave guiding part. The wave guiding part is an optical component system that changes light emitted from a light emitting lamp to a uniform surface light source, including a reflective plate, a diffusion plate and a prism sheet. The light emitting part includes the light emitting lamp, an inverter that supplies power to light emitting lamp, and a shield cover that protects the inverter.
FIG. 1 is an exploded perspective view of a general direct type LCD.
As shown in FIG. 1, the LCD includes a direct type backlight unit 20 that provides light to a liquid crystal panel 10 that displays a screen image.
The liquid crystal panel 10 includes a TFT substrate, a color filter substrate, and liquid crystal injected between the two substrates. Also, the liquid crystal panel 10 includes a data PCB, a gate PCB, a TCP (Tape Carrier Package) of a data side, and a TCP of a gate side.
The backlight unit 20 includes a lamp unit 21 that generates first light, a reflective plate 23 that reflects the first light generated from the lamp unit 21, and a light adjusting unit 22 that diffuses the first light to output second light having a uniform luminance distribution.
The lamp unit 21 includes one or more lamps 212a, lamp holders 21b installed at both end portions facing the one or more lamps 21a, and an inverter that supplies power to the lamp unit 21. An inverter PCB 50 having an inverter circuit is covered by a shield cover 60 and fastened to a rear surface of a lower cover 25.
The light adjusting unit 22 includes a diffusion plate 22a, and a first diffusion sheet 22b, a prism sheet 22c, a second diffusion sheet 22d, etc. which are sequentially disposed at an upper side of the diffusion plate 22a. 
A main support is formed at an upper portion of the backlight unit 20 and at a lower portion of the liquid crystal panel 40, maintaining the balance of overall power of the LCD.
The upper cover 40 surrounds the edges of four sides of the liquid crystal panel and is fastened to the lower cover 25 to accommodate the liquid crystal panel 10 and the backlight unit 20.
FIG. 2 is a view showing a state that the inverter PCB and the shield cover are fastened to the lower surface of the lower cover, and FIG. 3 is a sectional view taken along line A-A′ in FIG. 2.
As shown in FIGS. 2 and 3, the inverter PCB 50 is disposed at one edge portion of the rear surface of the lower cover 25, and includes an inverter IC (Integrated Circuit) 50a including an integrated element such as an FET, etc., and a transformer 50b. 
The shield cover 60 is positioned at an upper portion of the inverter PCB 50 to protect the inverter PCB 50 against external static electricity and includes a plurality of holes formed on its surface to externally release heat generated from the lower inverter PCB 50.
Recently, as the LCD is increasingly enlarged, it uses more backlights employing a high output transformer for voltage transformation, and in this case, a large amount of magnetic flux is induced to the shield cover 60 to cause eddy current, which results in that the system generates heat of high temperature and much power consumption.